A 50 V, 300 A modular water-cooled DC power supply with high availability for solid state RF amplifier |
Overview
A 50 V, 300 A modular water-cooled DC power supply having both DC and pulse loading capability is designed, developed and demonstrated for biasing solid state RF amplifier. This power supply employes two nos. of 50 V, 150 A water-cooled DC power modules and one no. of active redundant power module, operating in parallel in master slave configuration to form a 300 A DC bus. From this DC bus, multiple nos. of individual power amplifiers of solid-state RF amplifier can be fed. This scheme also facilitates the easy replacement of faulty power module. In this scheme, both DC power supply and RF amplifiers are independent and redundancy can be incorporated in DC power supply and RF amplifies independently. The heat load to ambient from this power supply is significantly reduced due to water cooling of its 50 V, 150 A DC power module. This power supply achieves availability of the order of 99.999% due to incorporation of redundancy and is suitable for round the clock operation in 24x7 mode. Its current THD is observed as < 30%, output voltage ripple is observed as ≤ 175 mV, output voltage stability is observed as ≤ 0.8% and overall efficiency is observed as ≥ 90% at 50 V, 300 A DC operating point.
Application: Suitable for simultaneously biasing individual power amplifier (PA) modules of solid-state RF amplifier, operating in CW as well as pulsed mode
Quick View Leaflet
Solid-state RF amplifier (SSA) with pulse capability demands following requirements from their DC bias power supply.
1. Very high availability for round the clock operation.
2. Operation in DC as well as pulsed mode of SSA.
A 50 V, 300 A water cooled DC power supply with 2 numbers of parallel connected 50 V, 150 A DC power modules and one active redundant power module to form a 300 A DC bus, is employed for simultaneously biasing multiple power amplifier (PA) modules of SSA. All parallel connected power modules are operated in master slave mode. The master power module is operated in constant voltage (CV) mode, while slave power modules are operated in constant current (CC) mode. Master power module controls the current sharing among all parallel connected power modules. The module controller of individual DC power module employs a proportional integral derivative (PID) voltage controller (CV loop) to regulate the output voltage of a 50 V, 150 A DC power module and a current control proportional integral (PI) controller (CC loop) to limit the output current of this power module.
Salient features of 50 V, 300 A water-cooled DC power supply:
- The power supply achieves very high availability in the order of 99.999% due to employment of highly reliable power modules and incorporation of one active redundant power module.
- This power supply is capable of feeding to both CW and pulsed RF load. The peak-to-peak amplitude of undershoot and overshot is limited to < 2.5 V during pulse loading.
- Heat dissipation to the ambient is reduced to water cooling of power modules. Major heat dissipating components are mounted on water-cooled heat sink.
- In the adopted scheme, there is wide flexibility for increasing the output current capacity of power supply by connecting more nos. of slave power modules in parallel.
- This power supply has online swapping feature where any faulty power module can be replaced online without affecting the operation of either power supply or RF amplifier.
Detail Technical Brochure
INTRODUCTION
Solid-state RF amplifier (SSA) offers many advantages over their vacuum tube counterparts like modularity, graceful degradation, requirement of low voltage DC bias power supply, no vacuum requirement, no warm up time, low maintenance and increased system availability. The use of separate power supply for individual power amplifier (PA) modules of SSAs is a common practice for RF applications of particle accelerators. In this scheme of biasing individual PA module with individual DC power supplies, the reliability of overall RF amplifier system decreases due to increase in the number of power supplies. In this configuration, the failure of individual DC power supply results in tripping off of the complete system as normally the DC health status contacts of all the power supplies are connected in series. Other major drawback of this scheme is that current THD in this power supply is considerably higher and electrical utility is not utilized efficiently.
In the adopted scheme, a low voltage DC power supply having high current DC bus is used for simultaneously biasing individual PA modules of high power SSA. In this case both DC bias power supply and RF amplifier are independent. The failure of either power supply (PS) module or PA module does not affect the operation of each other and redundancy can be incorporated in both of them independently. A 50 V, 300 A water cooled DC power supply employing two numbers of 50 V, 150 A water cooled DC power modules and one redundant power module is developed for biasing 16 numbers of 500 W (PA) modules of 5 kW SSA. In this power supply, parallel connected power modules form a 300 A DC bus.
Various measures are taken to increase the availability of this power supply. A two-switch forward converter topology employing only two semiconductor IGBT switches are employed in its 50 V, 150 A water cooled DC power module. In this topology, as input voltage of IGBT switches is clamped so no snubber circuitry is required, making this topology much simpler and reliable. Efforts are taken to minimize switching stresses of crucial power components. Power components of adequate voltage and current ratings from reputed manufacturers are employed in this power module. One power module is kept as active redundant to increase the power supply availability. Again, this power supply has online swappable feature, which facilitates the online replacement of its faulty power modules and further improves the availability of this power supply significantly.
This power supply is suitable for pulse operation of RF amplifiers. The output filter capacitors of individual 50 V, 150 A DC power modules are increased to limit the droop in DC bus voltage during load pulsing and control loop of individual power module is tuned in such a way that it minimizes the overshoot and undershoot during pulsing of solid state RF amplifiers. It is tested with 5 kW, 505.8 MHz SSA for continuous 8 hours of operation in both CW and pulse mode. The power supply performed satisfactorily during testing in both CW and pulse mode operation of RF amplifier. In pulse mode of testing, the peak-to-peak amplitude of undershoot and overshoot in the output DC bus voltage was observed as < 2.5 V, which is quite satisfactory for RF amplifier operation.
Technical specifications
Sr. No. |
Technical parameters |
: |
Values |
1. |
Input line voltage |
: |
3-phase, 4 wire, 440 V AC (± 10%), 50 Hz |
2. |
Nominal output voltage |
: |
50 V DC |
3. |
Maximum rated output current |
: |
300 A continuous |
4. |
Output voltage ripple |
≤ |
175 mV (peak to peak) at 50 V for load variations from 10% to 100% load |
5. |
Output voltage stability (long term) |
≤ |
400 mV for 8-hour duration at ambient temperature |
6. |
Efficiency |
≥ |
90% (for load current varying from 260 A to 300 A at 50 V DC) |
7. |
a) Total harmonic distortion in input current (ITHD) b) Input Power factor |
≤
≥ |
30% (for load current varying from 260 A to 300 A at 50 V DC) 0.9 (lagging) at full rated output |
8. |
Protection |
: |
Output over voltage, output under voltage, output over current and output short circuit |
9. |
(a) Cooling
(b) Inlet water temperature (c) Maximum flow rate of water (d) Inlet pressure (maximum) (e) Typical inlet pressure (f) Maximum pressure drop |
:
: : : : : |
Low conductivity water (or purified water) cooling 28ºC ± 2ºC 7.5 lpm 10 kg/cm2 6 kg/cm2 3 kg/cm2 |
10. |
Heat load to ambient at 50 V, 300 A DC output |
≤
|
550 W |
11. |
Availability of 50 V, 300 A water cooled DC power supply |
≥ |
99.999% |
INFRASTRUCTURE
- The water chiller having capability to supply at least 7.5 lpm flow rate of purified water at maximum inlet pressure of 10 kg/cm2.
- Reliability, Availability and Maintainability Software for estimating the Mean Time between Failure (MTBF) of power modules and availability of power supply.
- Measuring instruments like power analyzer, current sensor, thermal sensor, DC contactor of 300 V, 500 A rating, voltage probes, current probes, oscilloscope, multimeters, Meggar, etc. Various sources of measuring instruments are commercially available for the manufacturer to augment the infrastructure.
- Trained professionals having technical background and expertise in the fields of low voltage, high current power supplies, power converters, high frequency (HF) transformers and control-protection system, etc.
SPACE
- Floor area ≥ 250 square feet
MANPOWER
- Technical Officer (Degree in Electrical/Electronic Engg.): 1
- Technical Supervisor (Diploma in Electrical/Electronic Engg.): 1
- Operators/Technician (ITI) :1